Over recent years, high quality printed images have been greatly demanded, even for copiers and printers employing electrophotography, specifically for the copiers and the printers for color images.
To obtain high quality images, it is known to be effective to decrease the particle diameter of a toner. In order to realize this, a variety of so-called chemical toners have been proposed. However, it has been difficult to say that such toners could realize sufficient color reproduction. The reason is that, since copiers and printers employing electrophotography have become widespread mainly in common office and for official document applications, light stability has been emphasized in toners from the viewpoint of obtaining long-term stability of printed images, whereby toners employing organic pigments as colorants have been commonly produced.
Namely, organic pigments are usually superior in heat resistance and light stability compared to those of dyes. However, organic pigments exhibit a lower chroma. Accordingly, toners employing organic pigments tend to exhibit a narrower color gamut (color reproduction range).
Further, in a color image formed via a subtractive color mixing method in which coloration is carried out with the reflected light of the three primary colors of yellow, magenta, and cyan, the color gamut thereof is narrow as compared to a color image observed on a display panel formed with an additive color mixing method. Thereby, there has been noted the problem that color data edited on a display panel could not be precisely reproduced on a printed material.
Assuming that it is effective to use a magenta toner exhibiting a high chroma is effective to solve this problem, use of a magenta toner exhibiting a high chroma has been proposed (for example, refer to patent Document 1).
However, even with such a magenta toner, reproduction of magenta or blue equivalent to those observed on a display panel has not been enough. The reason is that magenta is inherently a complementary color of green and the reflectance spectrum of magenta ideally has a hue angle having a good balance between a blue component and a red component, but the above magenta toner has an insufficient blue component, resulting in exhibiting a poor balance.
Further, since the magenta colorants used for such a magenta toner exhibit poor pulverization properties, it is difficult to obtain a particle diameter not more than a prescribed value, even using a wet-type pulverizer, whereby a magenta colorant in magenta toner particles has poor dispersibility. Accordingly, the magenta colorant tends to be unevenly distributed on the surface of the magenta toner particles, whereby weakly charged toner particles with an insufficient charging amount or excessively charged toner particles, which are excessively charged, are formed. Therefore, the weakly charged toner particles exhibit poor adhesion to a frictional charge-providing member such as carriers or a development roll, resulting in a tendency to cause ‘toner scattering’ (also referred to as ‘toner cloud’ or “flying toner”). In contrast, the excessively charged toner particles exhibit excessively strong adhesion to the frictional charge-providing member, therefore, the toner particles remain in the system without leaving, whereby frictional charging to be conducted by a freshly fed toner and the frictional charge-providing member may be prevented. Accordingly, the freshly fed toner scatters in the machine without being charged. As the result, in cases of long-term use, the optical sensors in the machine become contaminated due to toner scattering, resulting in the possibility of causing malfunctions or shutdown of the apparatus.    Patent Document 1: Japanese Patent Application Publication Open to Public Inspection (hereafter referred to as JP-A) No. 5-11504